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At least 163 records · Page 9Linked to original sources
PubMed1999

Possible effects of sunlight on human lymphocytes.

The human population is exposed to both the ultraviolet A (UVA) and B (UVB) regions of the solar spectrum. UVB induces mainly dipyrimidine photoproducts in DNA by a direct photochemical mechanism, whereas UVA is absorbed by other cellular constituents and induces mainly oxidative damage indirectly. The proportions of the different dipyrimidine photoproducts, and the ratio of dipyrimidine to oxidative damage depend on the exact spectral output of a UV source. Irradiation of human epidermal keratinocytes induces release of cytokines, with cyclobutane pyrimidine dimers playing a significant role in the process. These cytokines may then modulate the activity of cells of the immune system. Freshly isolated human lymphocytes are exquisitely sensitive to UVB irradiation, because of their low deoxyribonucleotide pools. They also have a separate defect in removal of cyclobutane pyrimidine dimers from their DNA. We have observed that frequencies of mutations at the hprt locus in human T-lymphocytes and translocations involving the bcl2 locus in B-lymphocytes appear to be associated with sunlight levels over the period before the blood sample was taken. This may be an indirect cytokine-mediated effect, and may be relevant to the possible link between non-Hodgkin's lymphoma and sunlight. On the other hand, sunlight can have beneficial effects, and may protect against autoimmune diseases including type I diabetes and multiple sclerosis.

Cell Transformation, Neoplastic↗
PubMedDate not supplied

Awareness, attitudes and behaviour of teenagers to sunlight.

Most campaigns for the prevention of skin cancer have detected more new cases and decreased the number of advanced cancers. Since the incidence of skin cancer continues to increase, however, we believe that primary prevention is the best way to control it. It must be kept in mind that sunlight exposure is the main changeable risk factor for skin cancer and that this exposure is most significant in childhood and adolescence. Our aim in this study was to evaluate the need for a campaign and design one if necessary. We therefore proposed to determine the level of awareness and the behaviour of students with respect to sunlight exposure. We surveyed 628 teenage students from 9 high schools in the city of Granada (Spain). The questions were grouped into four sections: 1. Relationship Sun and Skin, 2. Relationship Sun and Environment, 3. Relationship Sun and Health, 4. Evaluation of Attitudes and Behaviour. More than 60% of the students gave satisfactory answers with regard to awareness, in contrast to the responses for attitudes and behaviour. Prevention campaigns for students are definitely necessary, keeping in mind in their design that a high level of awareness does not translate into healthy habits with regard to sunlight. Intervention to change behaviour patterns should be the main goal of primary prevention campaigns.

Adolescent↗
PubMed2001

Sunlight and the 5-year incidence of early age-related maculopathy: the beaver dam eye study.

OBJECTIVE: To investigate the relation of sunlight exposure and indicators of sun sensitivity with the 5-year incidence of early age-related maculopathy (ARM). DESIGN: Longitudinal, population-based study. Participants (aged 43-86 years at baseline) in the Beaver Dam Eye Study were reexamined from 1993 to 1995, 5 years after the baseline examination. Questionnaire data about sunlight exposure and sun sensitivity were obtained at baseline. Additional information about earlier life patterns of exposure was ascertained at follow-up. Stereoscopic color fundus photographs were graded to determine the presence of ARM at the 5-year follow-up in eyes free from signs of early ARM at the baseline examination. RESULTS: Leisure time spent outdoors while persons were teenagers (aged 13-19 years) and in their 30s (aged 30-39 years) was significantly associated with the risk of early ARM (odds ratio, 2.09; 95% confidence interval, 1.19-3.65). There was a slight, but nonsignificant, protective effect associated with use of hats and sunglasses while persons were teenagers and in their 30s (odds ratio, 0.72; 95% confidence interval, 0.50-1.03). People with red or blond hair were slightly more likely to develop early ARM than people with darker hair (odds ratio, 1.33; 95% confidence interval, 0.97-1.83). There were no associations between estimated ambient UV-B exposure or markers of sun sensitivity and the incidence of early ARM. CONCLUSION: Exposure to sunlight may be associated with the development of early ARM.

Adult↗
PubMed1953

BCG-vaccine studies. 6. Effect of exposing the vaccination site to sunlight immediately after vaccination.

Early in 1953, nearly 2,000 schoolchildren in Jabalpur, India, were tuberculin-tested, and 1,200 of them vaccinated, in a co-operative study designed to determine whether exposing the vaccination site to strong sunlight immediately after injection of BCG would affect the development of tuberculin allergy. Follow-up examination in 5-6 weeks showed that the tuberculin reactions (and vaccinal lesions) averaged the same size in three groups of vaccinated children: (a) those whose vaccination site was exposed to sunlight for a period ranging from 0 to 45 minutes immediately after vaccination; (b) those exposed for a full 45 minutes after an interval ranging from 0 to 45 minutes after vaccination; and (c) those not exposed during the study period. It would thus appear unnecessary at the present time to recommend shielding the vaccination site from sunlight immediately after the vaccine has been injected.

BCG Vaccine↗
PubMed2003

[Effects of sunlight and temperature on ultrastructure and functions of chloroplast of cucumber in solar greenhouse].

Studies on the effects of sunlight and temperature on the ultrastructure and functions of leaf chloroplasts of cucumber (Cucumis sativus L.) in solar greenhouse showed that the size of cells, chloroplasts, and starch grains and the number of chloroplast, grana, grana lamella and grana thickness of leaf chloroplast of cucumber increased with lowering leaf position. The microstructure of leaves and the ultrastructure of chloroplast of cucumber leaves were different because of the difference of temperature and sunlight among different months. In January, the light intensity was lower, and the cell size of cucumber leaves was larger than that in May, but the number of chloroplasts was less than that in May. The relationships between photosynthetic rate (Pn) and ultrastructure of chloroplast of cucumber leaves were not direct and very close. The Pn of the fourth leaf of cucumber was the highest, that of the first spreading out leaf was the second, and the near ground leaves had the lowest Pn. The primary reasons of the difference of Pn among different position leaves were that the leaf age and accepted light intensity were different. If different position leaves of cucumber accepted the same sunlight intensity, the difference of Pn among leaves of different positions would be smaller. Less efficient light hours and lower light intensity were the main factors influencing cucumber growth and yield in solar greenhouse. Comparatively, under sunny circumstance, the restriction of temperature on cucumber growth was very small, but in cloudy days, lower temperature induced by low light intensity became a key factor that restricted cucumber growth.

Chloroplasts↗
PubMed1991

[Excision repair does not protect Bacillus subtilis cells from inactivation by sunlight].

Exponentially growing Bacillus subtilis cells are highly sensitive to inactivating action of sunlight, the strain deficient in excision repair being every more sensitive than the uvr1 mutant. The inactivating effect is connected with the action of irradiation located in the left part of the spectrum (the whole UV region and some zones of the visible one). Increased sensitivity to sunlight disappeared when cells were exposed to sunlight in a liquid medium with casaminoacids (2 g/l). The inactivating effect was probably of photodynamic nature and was caused either by DNA lesions that were not removed by excision repair or by the damage which arose not in DNA.

Bacillus subtilis↗
PubMed1988

Health effects of sunlight exposure in the United States. Results from the first National Health and Nutrition Examination Survey, 1971-1974.

The dermatologic component of the first National Health and Nutrition Examination Survey (N = 20,637), conducted from 1971 through 1974, documented the deleterious effect of ultraviolet radiation on selected skin and eye conditions. Actinic skin damage was more frequent in white men with high as compared with low sunlight exposure, 36.7% vs 23.3%, respectively. Among white women, the corresponding figures were 34.1% vs 18.6%, respectively. Actinic damage was found more often in individuals with light eye color. Basal cell epitheliomas were found in 11.3% of white men aged 65 to 74 years who had severely actinic-damaged skin as compared with 1.0% of those with undamaged skin. Sunlight exposure was positively associated with localized hypomelanism, localized hypermelanism, seborrheic keratoses, senile lentigines, freckles, acne rosacea, spider nevi, varicose veins, venus star, dry skin, wrinkled skin, pterygia, arcus senilis, and a variety of minor oral lesions of the tongue, palate, and buccal mucosa. These findings suggest that a large number of dermatologic conditions, which may in part result from overexposure to sunlight, may be preventable.

Adolescent↗
PubMed1977

Photochemotherapy of psoriasis using methoxsalen and sunlight. A controlled study.

Fifty-one patients with psoriasis were treated with oral methoxsalen and sunlight exposure. Twelve of these patients received either methoxsalen or placebo prior to whole-body exposure. The remainder were treated with methoxsalen and sunlight to one side of the body and sunlight alone to the other. The conventional dose of methoxsalen (0.6 mg/kg) was compared with a low dose (0.3 mg/kg). Oral methoxsalen when used in the higher dose followed by sun exposure is an effective treatment for psoriasis. Accurate ultraviolet dosimetry is essential to avoid phototoxic burns. The advantages and disadvantages of solar photochemotherapy are discussed.

Clinical Trials as Topic↗
PubMed1983

Alteration of T cell subsets and induction of suppressor T cell activity in normal subjects after exposure to sunlight.

The effects of exposure to natural sunlight on the immune system were studied in 15 normal human subjects. Exposure was for 1 hr each day for 12 days over 2 wk and tests were carried out before, on completion, and 2 wk after completion. In comparison to concurrent studies on 13 age- and sex-matched controls, sun-exposed subjects had a significant increase in their circulation of T cells recognized by OKT8 monoclonal antibodies and a decrease in OKT4 positive T cells. Suppressor T cell activity measured in pokeweed mitogen-stimulated cultures of T and B cells was significantly increased against IgG and IgM production. These changes were still evident in many of the subjects 2 weeks after completion of the sun exposure. A trend for depression of natural killer cell activity against a melanoma target cell was noted in the present study, but this did not appear as marked as that noted previously in subjects exposed to radiation in solariums. The differences between the effect of radiation from solariums and natural sunlight on the immune system may result from the higher dosage of UV-A in radiation from solariums. The results suggest that exposure to sunlight may favor the induction of suppressor pathways in response to antigenic stimuli and that this may limit immune responses against tumor cells such as melanoma. They support the idea from animal studies that systemic changes in the immune system may be an important factor in the association of UV radiation with malignancy.

Adult↗
PubMed1980

Acne vulgaris aggravated by sunlight.

The symptoms of approximately 3 percent of our patients with acne vulgaris worsen during the summer months even though they maintain previously effective therapy. We show herein that the addition of 5 percent para-aminobenzoic acid (PABA) in alcohol (used as a sunscreen) resulted in marked improvement in their ability to tolerate sunlight. This condition, acne vulgaris aggravated by sunlight, has been compared to acne aestivalis which is another sunlight-induced disorder.

Acne Vulgaris↗
PubMed1983

Carcinogenic effect of sequential artificial sunlight and UV-A irradiation in hairless mice. Consequences for solarium 'therapy'.

The carcinogenic effect of artificial UV sunlight followed by UV-A irradiation in human solaria doses has been studied with the use of the hairless mouse as an animal model. Artificial sunlight exposure alone induced only a moderate skin tumor incidence (animals with at least one tumor) of 0.15 after one year, and UV-A irradiation alone induced no tumor formation. However, the combination of artificial sunlight exposure and subsequent UV-A irradiation significantly increased the tumor incidence to 0.72. We conclude that, in humans, tanning with UV-A for cosmetic purposes may not be an innocuous procedure.

Animals↗
PubMed1997

Sunlight induces pyrimidine dimers preferentially at 5-methylcytosine bases.

The most prevalent DNA lesion induced by UV irradiation is the cyclobutane pyrimidine dimer (CPD), which forms at positions of neighboring pyrimidines. Here we show that the rare DNA base 5-methylcytosine is the preferred target for CPD formation when cells are irradiated with natural sunlight. We have mapped the distribution of CPDs formed in normal human keratinocytes along exons of the p53 gene. Codons 196, 245, 248, and 282, which are mutational hot spots in skin cancers, are only weakly to moderately susceptible to formation of CPDs after irradiation with UVC (254 nm) or UVB (320 nm) light sources. However, when cells were exposed to natural sunlight, CPD formation was enhanced up to 15-fold at these codons due to the presence of 5-methylcytosine bases. These results suggest that CPDs containing 5-methylcytosine may play an important role in formation of sunlight-induced skin tumors and that methylation of CpG sequences, besides being involved in spontaneous mutagenesis processes, can also create preferential targets for environmental mutagens and carcinogens.

5-Methylcytosine↗
PubMed1998

[Adverse effects of sunlight on the skin].

Many people consider a summer's day pleasant: warm and bright. The sun's ultraviolet rays do not contribute to the pleasure, and are biologically mainly harmful. As UV radiation does not penetrate any deeper than our skin, this organ has to be particularly well adapted to the UV exposure. The skin exploits the UV radiation for the synthesis of vitamin D3. Our day-to-day exposure suffices for this beneficial UV effect. Excessive exposure, as in sunbathing, only contributes to the adverse effects, like sunburn and suppression of cellular immunity in the short term, and 'photoaging' and skin cancer in the long term. The UVB radiation in sunlight is mainly responsible for these harmful effects, the UVA radiation to a far lesser extent (10-20% contribution). The UVA radiation from modern tanning equipment does not differ from that in sunlight, but UVA radiation does not lead to vitamin D3 production; it rather degrades vitamin D3 and a tan offers insufficient protection against the UVB radiation in full sunlight.

Cholecalciferol↗
PubMed2000

Heteroflocculation of Amidine Polystyrene Latex and Anticarsia gemmatalis Nucleopolyhedrovirus as a Model System for Studying Sunlight Protection.

Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) is a baculovirus specific for the control of an important soybean defoliator. The baculovirus is comprised of double-stranded DNA, occluded in a proteinaceous structure called a polyhedron. Ultraviolet sunlight is the most destructive factor that affects the persistence of the virus in the field. In the present study, we use a model system wherein the pathogen is covered by another particle of opposite charge in order to test the effectiveness of a physical barrier as a protection against sunlight. Heteroflocculation experiments were carried out using two different age batches of AgMNPV and amidine polystyrene latex particles. The assessment of heteroflocculation was achieved by zeta potential and adsorption isotherm measurements, and by scanning electron microscopy. Despite the great difference in potentials between latex particles and the baculovirus, low-affinity isotherms were obtained in both pure water and 0.1 mM KCl. Adsorbed latex particles were easily washed out from the polyhedron surface. This low affinity could be attributed to the presence of a strongly repulsive hydration force of short range operating on the system. The results suggest that the failure to obtain a good physical barrier against sunlight might be attributed to the difficulty in keeping the polyhedron surface covered. Copyright 2000 Academic Press.

Journal Article↗
PubMed1993

Sunlight-induced mutagenicity of a common sunscreen ingredient.

We have tested the mutagenicity of a UV-B sunscreen ingredient called Padimate-O or octyl dimethyl PABA, which, chemically speaking, is identical to an industrial chemical that generates free radicals when illuminated. It is harmless in the dark but mutagenic in sunlight, attacking DNA directly. A commercial sunscreen containing Padimate-O behaves in the same way. UV-A in sunlight also excites Padimate-O, although less than UV-B. Some related compounds, including a known carcinogen, behave similarly. As mutagens may be carcinogenic, our results suggest that some sunscreens could, while preventing sunburn, contribute to sunlight-related cancers.

4-Aminobenzoic Acid↗
PubMed1999

Simulation of the daily sunlight illumination pattern for bacterial photo-hydrogen production.

Methods of illumination to simulate the daily sunlight irradiation pattern were studied in relation to photohydrogen production using the photosynthetic bacterium Rhodobacter sphaeroides RV. Three illumination patterns were compared, in which the light intensity was changed in 1, 3, or 6 steps. As a control, outdoor experiments were also carried out over a 3-d period in Tsukuba, August 1996. Outdoors, hydrogen production by Rba. sphaeroides RV was dependent on the sunlight intensity: the total volume of hydrogen produced per day varied from 14 to 28 l.m(-2), while the total light energy ranged from 5.5 to 6.4 kWh.m(-2). d(-1). The maximum hydrogen production rate was 2.8 l.m(-2).h(-1) under a 4.5-cm light path and the average light energy conversion efficiency was 1.1%. Indoors, the hydrogen production rate was found to be independent of the mode of illumination among the three patterns employed. The maximum hydrogen production rate was 3.3 l.m(-2).h(-1) with a light energy conversion efficiency of 1.0%, and it was concluded that the single-step illumination method provides an appropriate simulation of sunlight. Saturation of hydrogen production occurs during high light intensity around noon and this plays a key role in the simulation.

Journal Article↗
PubMed1998

Effects of Sunlight Illumination of Marigold Flower Meals on Egg Yolk Pigmentation.

The effect of sunlight illumination of marigold flower meal on the pigmentation of feed for laying hens and of their resulting egg yolks was evaluated by high-performance liquid chromatography and by subjective and light reflectance colorimetry techniques. Illumination did not have an effect on the identity of carotenoids in the flower meal. Interestingly, illuminated marigold flower meals yielded an oleoresin with a higher all-trans-zeaxanthin level, with respect to meals kept in darkness. A higher level of all-trans-zeaxanthin was also present in feed pigmented with that oleoresin. Additionally, this pigmented feed showed the best color values and resulted in egg yolks with good color; remarkably, these egg yolks had a low pigment content with respect to control treatments. Thus, sunlight illumination of marigold flower meal showed a positive effect on egg yolk color; the main factors contributing to this effect were not the identity or quantity of carotenoids in laying hen feed or egg yolks, but rather other as yet unidentified marigold component(s) which was (were) somehow influenced by sunlight illumination.

Journal Article↗
PubMed1994

Sunlight inactivation of enterococci and fecal coliforms in sewage effluent diluted in seawater.

Inactivation (loss of culturability) by sunlight of enterococci and fecal coliforms within sewage effluent diluted in seawater was investigated in field experiments. In most experiments, 500-ml flasks of pure silica were used to confine activated sludge effluent diluted to 2% (vol/vol) in seawater. Inactivation of bacteria in these flasks (diameter, 0.1 m) was faster than in either open chambers (depth, 0.25 m) or patches of dyed effluent (depth of order, 1 m), probably because of the longer light paths in the latter two types of experiment, which caused greater attenuation of sunlight. Inactivation of 90% of enterococci generally required 2.3 times the insolation required for 90% inactivation of fecal coliforms, because of both the presence of larger initial shoulders on survival curves and a lower final inactivation rate. Two parameters are required to model inactivation of enterococci, a shoulder constant as well as a rate coefficient. The depth dependence of inactivation rate for both fecal indicators matched the attenuation profile of UV-A radiation at about 360 nm. Inactivation by UV-B radiation (290 to 320 nm), which penetrates much less into seawater, is of minor importance compared with the UV-A and visible radiation in sunlight, contrary to expectations in consideration of published action spectra for bacterial inactivation.

Journal Article↗